1. Technical Field
The present invention relates to a power amplifier, and more particularly to a multi-mode power amplifying circuit, and a multi-mode wireless transmission module and method thereof.
2. Related Art
In a wireless communication system, power amplifier is the located at the end of a transmitter. When a small modulated signal is input into power amplifiers, the power of the small modulated signal is amplified by single or multi-stage power amplifiers so as to output a power that complies with required specification.
With the different signal modulations in the wireless communication system, different specifications of transmitters are required and each specification requires different output power. For wireless network standards (for example, 802.11abg standard), the orthogonal frequency-division multiplexing (OFDM) technology is used, which is similar to the amplitude modulation (AM) technology, requiring a high-linearity power amplifier, where the transmission belongs to middle/long distance transmission. Bluetooth technology is mainly applied to short distance transmission, and therefore requires a low-power-consumption power amplifier for low power transmission.
In recent years, communication devices have developed to support multiple wireless transmission technologies; for example, the wireless network standards and Bluetooth technology. To reduce the size of a wireless device, the transmitter is mostly designed to be applicable to high and low power transmission. Consequently, how to maintain an amplifying operation with high power efficiency during transmission at different output powers is one of the issues when designing a power amplifying circuit.